1. Field of the Invention
The present invention relates to a device for controlling turn behavior of a vehicle so as to suppress and reduce undesirable behavior such as drift out or spin which can occur during turn of a vehicle such as an automobile.
2. Description of the Prior Art
As one of the devices for controlling behavior of a vehicle such as an automobile during turn of the vehicle, there is known an art such as described, for example, in Japanese Patent Laid-open Publication 5-278624, which comprises means for obtaining rate of change of yaw rate of the vehicle body, means for obtaining slip angle of the vehicle body, means for presuming turn behavior of the vehicle based upon the rate of change of the yaw rate and the slip angle, and means for controlling turn behavior of the vehicle based upon the presumed turn behavior to stabilize the turn behavior.
By such a behavior control device, as compared with an art presuming turn behavior of a vehicle based upon lateral acceleration of a vehicle body liable to be affected by the friction coefficient of road surface, it is possible to presume turn behavior of the vehicle at high precision, regardless of the friction coefficient of road surface, so that the turn behavior of the vehicle during a turn is controlled more desirably.
In the behavior control device described in the above-mentioned patent laid-open publication, the control of turn behavior of a vehicle is based upon the detection of lateral acceleration of a vehicle body, vehicle speed, and yaw rate of the vehicle body. However, since the control based upon the lateral acceleration and the yaw rate incorporates therein an integration procedure, errors in the detection of those parameters are accumulated, and therefore, the accuracy of the control is often damaged by the accumulation of those detection errors. Further, as the optimum points of standard values for comparison often shift during the judgement of the turn behavior due to changes of running conditions of the vehicle, the accuracy of the behavior control is also thereby damaged. Particularly when a spin of the vehicle is presumed in the control of the turn behavior of a vehicle such that braking forces applied to vehicle wheels are controlled based upon a presumed spin condition of the vehicle, if the judgment of the spin is not accurate, it can occur that the spin is augmented. However, if a non-sensitive area against errors is increased to accommodate such detection errors, the control of turn behavior of a vehicle will not be accomplished in a stable manner.